1. Field of the Invention
Embodiments of the present invention relate to honeycomb cores. More particularly, embodiments of the present invention relate to methods for creating honeycomb cores by welding a plurality of metal sheets together using a serpentine welding path.
2. Description of the Related Art
A honeycomb core is a structure formed from a plurality of cells that are joined together, wherein each cell may be open-ended with a plurality of walls that surround empty space. The honeycomb core is typically sandwiched between other materials to generally provide lightweight support strength over an area. Honeycomb cores may also be used for acoustic damping, energy absorption, and airflow direction. Honeycomb cores may be utilized in the aerospace, aircraft, automotive, marine, and railcar industries, among others.
One approach to creating honeycomb cores is to create a stack of sheets, where each sheet is bonded to the sheet beneath it, and the stack is expanded after bonding to form the core. In some cases, the sheet material may be non-metallic and the sheets may be bonded together with adhesive or epoxy. In other cases, the sheets may be made of metal foil and bonded together by welding. Each sheet may be welded to the sheet below with a plurality of parallel linear weld paths. Each weld path may cause a slight shrinkage in the foil along the weld path, which in turn may cause the foil to curl on the sides of the weld path. The curling may lead to an uneven welding surface and curvature of the stack of sheets near the edges. The curvature increases as the size of the stack grows. Depending on the design requirements, hundreds of metal sheets may be stacked and welded to create the honeycomb core. Since the integrity of the weld and the quality of the core may depend on the flatness of the welding surface, either the size of the core may be limited or flattening techniques may need to be applied.
When the curvature of the stack becomes excessive, a flattening process may be applied, wherein the stack may be removed from the welding station and placed in a vacuum furnace where it is weighted down and heated to flatten the curvature of the stack. Afterwards, more sheets may be welded to the stack until the curvature again becomes excessive and the flattening process is repeated. Correcting the curvature of the stack adds time and expense to the production of the honeycomb core.
An angled honeycomb core may have a face at an angle between zero degrees and ninety degrees with respect to the longitudinal axis of each cell. The angled honeycomb core may be used in thermal airflow applications where directional heat removal is required. One approach to creating an angled honeycomb core is to build a stack of bonded sheets, as described above. But before expanding the stack, the sides of the stack that form the faces of the core are cut at a wedge-shaped angle, corresponding to the desired angle of the core cells, and that portion of the stack is removed. Since the sides of the stack that form the faces are usually along the largest dimension of each sheet, cutting and removing the stack along the face sides wastes a large amount of core material.